Apparatus for abrasively treating metal objects



C. H. HAMMELL April 29, 1941. 2,239,714

APPARATUS FOR ABRASIVELY TREATING METAL OBJECTS Filed Jan. 29, 1937 5 Sheets-Sheet 1 INVENTOR C MRLES HAYWARD HAMMELL.

ATTORNEY April 29, 1941. c. H. HAMMELL APPARATUS FOR ABRASIVELY TREATING METAL OBJECTS,

Filed Jan. 29, 1937 5 Sheets-Sheet 2 INVENTOR C/mmzs HAYWARD Hmmu.

ATTO R N I ZY April 29, 1941- c. H. HAMMELL APPARATUS FOR ABRASIVELY TREATING METAL OBJECTS Filed Jan. 29, 1937 5 Sheets-Sheet 3 A ril 2 9, 1941- c. H. HAMMELL APPARATUS FOR ABRA SIVELY TREATING METAL OBJECTS Filed Jan. 29, 1957 s SheetsSheet ---INVENTOR ATTORNEY April 1941- c. H. HAMMELL. 2,239,714

APPARATUS FOR ABRASIVELY TREATING METAL OBJECTS Filed Jan. 29, 1937 5 Sheets-Sheet 5 7e INVENTOR OM15 Ham/r0 HAMMm.

ATTO RNEY Patented Apr. 29, 1941 UNITED STAT I APPARATUS FOR ABRASIVELY TREATING LIETAL OBJECTS Charles Hayward Hammcll, Mishawaka, had, as-

signer to The Americ Company, Mishawaka,

Delaware Application January 29 8 Claims.

This invention relatesto apparatus for abrasively treating metal objects.

In treating metal objects, such as castingsand forgings, with a stream of abrasive particles, for the purpose of cleaning, polishing, hardening or otherwise modifying the surface characteristics, it is generally desirable to expose all or predetermined portions of the surfaces of the articles sufficiently to the action of the stream of abrasive or other treating material to effect complete and uniform treatment. Where the articles are small, rugged and suitably shaped they can be convenientlyexposed for treatment in a tumbling mill or like apparatus. However, tumbling or the equivalent handling is not suitable in many instances, as for example, where the articles are large and heavy, delicate and brittle, irregularly or awkwardly shaped and have substantial projections, or where they have cavities of substantial depth. In addition, it is often desirableto expose the articles in a predetermined manner in order to insure a complete or a predetermined degree of treatment, which generally cannot be insured by tumbling.

Where relatively large quantities of articles are to be treated, it is desirable to pass them in succession through the abrasive stream in a more or less continuous series to avoid loss of time, power and labor, and to obtain the maximum utilization of the apparatus. Generally, maximum efliciency can best be obtained by providing partial or full automatic operation.

According to the present invention, the article to be treated is suspended by means of a suitable conveyor mechanism which interposes the minian Foundry Equipment Ind., a corporation of 1937, Serial No. 122,908

The present invention also provides suitable apparatus comprising the combination of one or more centrifugal throwing wheels having means for controlling the direction of flight of the thrown abrasive with a conveyor mechanism for carrying the articles tobe treated through a stream or streams. The'conveyor mechanism comprises a suitable track having a plurality of suspension devices traveling thereon, each adapted to carry, one or more articles to be treated in suspended position. The conveyor is suitably driven to advance the suspension devices along a predetermined path and through the stream or streams of abrasive, a suitable drive mechanism being provided to retard'or completely halt the forward movement of the suspension devices for a predetermined period when it is brought into the abrasive stream. Each suspension device is adapted to retard the article while in the stream or streams of abrasive, thereby permitting all portions of the article to be presented to the abrasive stream. Preferably, a suitable housing is. provided to enclose the abrasive streams which is provided with suitable entrance and exit openings. The driving mechanisms and like operating parts are disposed outside of the housing and are thus .protected from wearand damage which might result from contact with the abrasive material.

The present invention provides apparatus ,by

. which castings, forgings or other articles can be mum obstruction to the impingement of the abrasive or other treating material against the article. The article is transported along a predetermined path and into the abrasive stream whereupon the forward movement of th article is retarded or completely halted and the article is turned about in the abrasive streamto expose quickly and'eiiectively cleaned, polished hardened, or otherwise treated. The invention permits close control of the extent of treatment and insures that all the articles may be treated in a,

predetermined and uniform manner. The apparatus is rugged and durable and is suitable for continuous and semi-automatic 'or fully automatic operation.

Various other features and advantages of the form of apparatus suitable for carrying out the I 7 present invention;

fining a cleaning chamber Fig. 2 is a top plan view of the apparatus shown in Fig. 1, certain portions of the apparatus being shown in cross section for convenience of illustration;

Fig. 3 is a side elevational view of a of the apparatus shown in Fig. 1;

Fig. 4 is a vertical transverse sectional view of the apparatus taken along line 4-4 of Fig. 3;

Fig. 5 is an enlarged fragmentary view partially in cross section showing a portion of one of the suspension devices;

Fi 6 is an enlarged fragmentary side elevational view of a portion of the structure shown in portion Fig. 5; and

Fig. 7 is a schematic and partially diagrammatic View of a portion of the conveyor and the wiring diagram of the control system for the conveyor drive.

In the following description and in the claims, various details will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit. Like reference characters denote like parts in the several figures of the drawings.

In the drawings accompanying and forming part of this specification, certain specific disclosure of the inventionis made for purposes of explanation, but it will be understood that the details may be modified in various respects without departure from the broad aspect of the invention.

The present invention is particularly useful in the treating of articles which are relatively large and heavy and which cannot conveniently be tumbled and which have numerous cavities or projections. One example of such article is a cylinder block casting for automotive engines. For the purposes of illustration, such a casting (designated by the reference character E in the drawings) is shown in connection with the embodiment of the apparatus disclosed herein. However, it is to be understood that the apparatus, according to the present invention, is capa ble of use with numerous types of castings, forgings and other articles adapted to be suspended while undergoing cleaning treatment.

Referring now particularly to Figs. 1 to 4, the apparatus preferably includes a housing In de- The housing has an inlet |2 closed by a pair of inwardly swinging doors l3 suitably mounted on hinges l4 and an outlet l5 closed by swinging doors I6. mounted on hinges IT. The doors I3 and I6 are so mounted that they tend to swing to closed position and normally assume this position.

One or more abrasive projectors are associated with the housing for projecting streams of treating material for suitably treating the articles when in predetermined position in the chamber The present apparatus includes three such projectors, denoted by reference characters A, B and C. All of the projectors A, B andC may be similar, and for the purpose of illustration, only one is illustrated and described in detail herein.

Referring now particularly to Fig. 4, the pro- J'ector comprises a rotary centrifugal wheel having a plurality of spaced throwing blades 2| extending in a generally radial direction from the periphery of the wheel and terminating inwardly short of the center to define a central space 22. Positioned within the space 22 and fixed relatively to the blades 2| to rotate therewith is an impeller 23 havinga plurality of radially arranged vanes 24. A tubular control member 25 surrounds the impeller and is provided with an outlet opening 26. The control member 25 is mounted so as to be stationary relative to the impeller 23 and throwing blades 2| but it may be adjusted for the purpose of controlling the direction of flight of the abrasive.

The throwing blades 2| may be carried by spaced side plates 21, 21 secured together and carried by hub 28 which is mounted on a shaft 29 rotatable in bearings 30 suitably mounted on a mounting plate I9 and additionally supported by a bracket IS. The wheel 20 may be rotated by motor 3| connected by a suitable drive 32 to the shaft 29.

For convenience, the motor 3| and bearings 30 may be mounted on the mounting plate l9 which may be suitably secured on the upright wall of the housing |0 thereby permitting the motor and wheel to be removed from the housing as a unit. The wheel 20 is mounted adjacent and may project partially through an opening 38 in the plate l9 and the housing side wall. A suitable housing 33 may partially surround the wheel and may be removably attached to the plate IS.

The wheel 20 may be supplied with abrasive through a feed pipe 35 leading from the hopper 36 and extending through an opening 37 in the side plate 21. Upon energization of the motor 3|, the impeller 23 and throwing blades 2|, together with the side plates 21, 21' rotate as a unit, the control member 25 remaining stationary. Abrasive fed to the impeller 23 is thrown by the impeller vanes through the outlet opening 26 and into the path of the blades 2|. The abrasive is urged along the leading faces of the blades 2| and is projected from the blades adjacent the periphery of the wheel by combined centrifugal and rotary forces.

The wheel is rotated at sufiicient speed to project the abrasive from the wheel 20 at an abrading velocity and in a fan-like stream and in a controlled direction. The direction of flight and impingement pattern is determined by the shape and adjustment of the control member 25.

The stream produces an elongated and generally rectangular impingement pattern, and may extend over a wide angle depending upon the shape and size of the control cage opening and the distance of the wheel from the work. The direction of the stream may be controlled by suitable adjustment of the clock-dial position of the outlet opening 26 in the control cage.

Although the term abrasive is used herein to designate the treating material, the term is intended to include all suitable material, such for example, as cracked steel grit, smooth steel shot, quartz sand or other materials suitable for cleaning, polishing, smoothing, hardening or otherwise modifying the surface characteristics of the article to be treated.

Referring to Figs. 2 and 4, the several wheels A, B and C may :be spaced longitudinally along the cleaning chamber The wheels may also be disposed at different elevations whereby the streams a, -b and c projected by the wheels A, B and C respectively impinge against the article E at different angles. As will be seen from an inspection of Fig. 4, a suitable arrangement of wheels may be made so that all portions of the various surfaces will be treated during the course of the passage of the article E through all of the streams.

Referring now to Figs. 1, 3 and 4, the bottom wall 40 of the housing may be inclined to form a hopper for collecting spent abrasive and a screen 42 may extend across the bottom of the treating chamber II for screening out scale and other particles of foreign matter. The hopper wall 40 may extend to a pit M and may lead to the bottom of an elevator 43. The elevator 43 includes an endless belt 44 trained over pulleys 48 and 41 and carrying a plurality of lifting buckets 45. The elevator is driven by motor'48 connected by drive 49 to the pulley 41 and thus spent abrasive may be elevated to an abrasive cleaning cham-' ber 50 from whence it falls by gravity into an abrasive storage chamber 5|. The storage chamber 5Imay be connected by suitable conduits 52, 53 and 54 to the projectors A, B and C. One or more vents 55 may be provided in the housing top wall for drawing off dust and other finely divided material."

An article-conveyor, preferably of the overhead suspension type, is associated with the housing I for advancing articles to be treated therethrough. The conveyor may include upright members 60, longitudinal horizontal members BI and transverse horizontal members 62 suitably arranged and connected to form a rigid frame for supporting a track I55. The track95 preferably is bearing I04 carried on a cross member I05. The

shaft IOI may be retained in its bearings by collars I06 and IN or other suitable means. The sprockets I00 are positioned preferably at the corners of the generally rectangular figure defined by the track and the radius of each; sprocket I 00 preferably corresponds with the radius of the corresponding portion of the track 65; thus each sprocket I00 is in engagement with the chain end I4. The shaft I2 extends into an opening 11 in a bearing member 15 and is retained therein by a collar I6 secured to the shaft I2 cooperating with a shoulder I8. A thrust bearing I9 may be interposed between theshoulder I8 and the col- 1 lar I6 to minimize friction. The opening 11 may be closed by a plate 80 suitably secured as by one or more screws 8|.

The suspension device I0 may be suspended from the track 65 by a hanger plate 82 secured to the bearing member 15 and having a pair of rollcrs 83 rotatably mounted on pins 84 fixed to the plate. A second hanger plate'85 having its upper end spaced from and generally parallel to the hanger plate 82 and carries a pair of rollers83 similar to the first set 'of rollers. The hanger plate 85 has a generally Z-shaped cross section and is formed with a horizontal portion 86 and a depending portion 81, the latter of which is secured as by rivets 88 to the corresponding portion of the hanger plate 82.

A drive chain 90, which may be of the link type, may extend along the series of suspension devices I0 and may be connected to each of the devices by a bracket 92 suitably attached to one of the links 9| and to the horizontal portion or shoulder 88 of the suspension plate 85 as by welding or riveting. The chain 90 may be guided and may be supported intermediate the suspensiondevices 10 by a guide track 93' and carried by one or more hangers 94' depending from the horizontal members 62 of the frame.

The drive chain90 is trained around a plurality of sprockets I00 suitably mounted for rotation on the conveyor frame. Each sprocket I00 is mounted on a shaft IOI journaled in a lower bearing I02 carried on a cross member I03 and in an upper over a-substantial portion of the circumference of the sprocket. I

One or more of the sprockets I00 may be suitably driven to cause the chain 90"to move the suspension devices I0 along the track 65. A mo tor IIO may be mounted on'a plate III sup-' ported on the horizontal members 82 and may be connected through a suitable driving mechanism v I I2, preferablylof the speed reducing type,,tothe shaft IOI of the drive sprocket I00. Upon energization of the motor IIO, the connected drive sprocket I00 is rotated and thus causes the chain to draw'the suspensiondevices I0 along'the track v 65 and'through the treating chamber II. Referring to Fig. 4, provision is made for admitting the hook and'shaft portion of each suspension device "I0 to the housing I0. As previously described, the doors I3 and I6 are pivotally mounted and can be forced open by applying pressure thereto in the proper direction. Extending upwardly from the inletopening I2 is a slot 96 positioned to permit theshaft I2 of the suspension device III to pass through the end wall of the housing I0. An elongated slot 93 is formed in the top wall of the housing I0 longitudinally of the housing and in position to permit the shaft I2 to pass therealong and thereby permit'thesu spension device 10 to be moved relatively along the housing I0 with its lower end in the treating chamber II. The opening 93 maybe normally closed by a pair of flexible sealing members 94 clamped to the top wall of the housing clamping plates or members 95. The sealing members 94 permit the shaft I2 to pass along the slotv 93, but

owing to their resiliency, spring back into engagement closing the opening immediately upon the passing of the shaft I2. If desired, sealing arrangements similar to those ,provided'for the top slot 93 may be provided for the end slots 95. Suitable means may be provided for rotating the'suspension devices I0 throughout at least a portion of their travel and particularly during the time they are under treatment by the abrasive projecting devices A. B and C.

Referring now particularly to Figs. 5 and 6, each suspension element I0 may be provided with a gear I40 mounted on the shaft I2 and fixed against rotation by a suitable means, such as a key I. The gear I40 may be supported on the g and I45.

mounted on shafts I46, I41 respectively, which shaft as by-a pin I42.

Referring'now particularly to Figs. 2 and 4, there is provided an endless driving element, such as a' chain I43, trained over driving gears I44 The driving gears I44 and I are in turn are rotatably mounted in bearings I48 and I49. The chain I43 may be provided with guides I and I5I which may be supported on the top wall of the housing by brackets I52.

The drive chain I43 may be driven from a motor I which is connected through a suitable speedreducer I56 and drive I51 to the shaft I4'I.

It will be seen that when the chain I43 is driven in a direction indicated by the arrows in Fig. 2, it causes clockwise rotation (as viewed in Fig. 2) of all of the gears I40 which are in position to be engaged by the chain I43. This rotation is imparted to the corresponding hooks H and the articles E carried thereby.

The driving arrangement for the suspension devices is designed to retard or completely halt each suspension device successively opposite the several abrasive projectors A, B, C whereby the article carried by the suspension device is retained in'each abrasive stream a, b, c for a sufficient period to treat the article to the desired extent. In the present embodiment of the invention, the driving arrangement is arranged to completely halt the suspension device for a predetermined period adjacent each of the pro jectors. This halting is preferably accomplished by cutting off the supply of electric energy flowing to the motor I I0.

Referring now to Fig. 7, there is shown more or less diagrammatically one form of mechanism for intermittently halting the driving motor IIO. Supply conductors H5 and H6 are provided for connecting on an electric motor IIO toa suitable source of power. A main switch H1 is connected in circuit-with the motor as by conductors I I8, II9 leading to a movable contact I and conductors I2I, I22 leading from a stationary contact I23 to the motor IIO. A return conductor I23 leads from the motor IIO to the supply conductor II6.

The switch I I1 preferably includes a spring I25 or equivalent means for normally biasing the movable contact I20 into engagement with one or the other of the stationary contacts I23 and I21. An actuating arm I26 may be mechanically connected to movable contact I20 and lies in the path of the suspension member 10 for actuation thereby. Preferably, the actuating, arm I26 is positioned to be engaged by the plate 82 of each suspension member 10 and to be rotated to move the contact I20 away from the contact I23 and into engagement with a stationary contact I21.

The timing mechanism I28 may be provided I for closing the motor circuit a predetermined interval' after the main switch I I1 has been opened, "therebycausing .the motor to move the suspension device v10 away from the switch I I1 and thus permittingtheswitch II1 to again close on the .flcontact I23,

The timing mechanism I28 may be of any suitable construction and may include a switch I3I by it is energized to close the switch with a delayed action, when the main switch H1 is closed on, the contact I21.

A pivoted reset lever I36 is connected as by a link I31 to the arm I26 for returning the con- .tact I20 to its initial position when the suspen sion device 10 passes. The operation of the tim I ing mechanism is as follows:

Assuming no suspension device 10 to be in engagement with the actuating arm I26, the switch H1 is closed on the contact I23 and the motor I I0 is thereby connected to the supply conductors H5 and H6 and is energized to move the susi li pension devices 10 along their path of move- 'ment.

and halting the motor. The contact I20, however, is snapped by the spring I25 and immediately closes on the contact I21 and completes a circuit through the relay I or other timing mechanism, which operates, after a predetermined interval, to close the switch I3 I The closing of the switch I3I completes a circuit through the motor and re-energizes the motor which thereby moves the suspension member 10 away from the actuating arm I26. As the suspension device 10 moves past the reset lever I36, the switch is thereby closed on the contact I23 and the circuit through contact I21and the solenoid I35 is broken.

The motor 0- continues to drive the suspension devices 10 until the next suspension device moves into engagement with the actuating arm I26 and the previously described cycle is again initiated. The relay I35 is made to act with sufficient delay so that each suspension device" 10 is halted for a suflicient time in position adjacent each projector to permit the work piece E to be exposed to the'stream for a sufllcient period to accomplish the desired treatment.

The general operation of the apparatus is as follows:

The supply conductors H5 and H6 are connected to a source of power and the motor H0 is thus energized to actuate the drive chain 90 and move the suspension devices 10 intermittently around the path defined by the track 65. The motor I55 is also energized to drive the chain I43, as above described.

The articles to be treated are placed on the hooks H at any convenient point along the path of movement of the suspension devices 10 and thereafter are carried by the suspension devices into the treating chamber II. As the suspension device approaches the inlet doors I3, the doors are forced open by the pressure of each suspension device 10 and its load to admit the article E and thereafter swing closed to completely seal the suspension chamber. The shaft 12 passes through the slot 96 andrides along the slot 93 without any substantial interference.

The control apparatus'is operated as above described and periodically halts the driving mechanism, thus causing the suspension devices 10 to halt in position for a predetermined period.'

The apparatus and control mechanism are so designed that each suspension device preferably hal-ts while opposite eachof the projectors A, B, 0, thus exposing the article E to the effect of eachfof the abrasive streams.

The driving chain I43 is adapted to engage each gear I prior to or at the time the first suspension device reaches its position opposite, the first abrasive projector A, thus causing the suspension device to be continuously rotated during the time it is opposite the'abrasive projector A. This rotation of the article E, combined with the divergent direction of several paths of the abrasive particles thrown by the projector A, causes the article E to be fully and completely exposed to the abrasive treatment.

The control mechanism then operates to actuate the driving'mechanism and advance the suspension member 10 to a position opposite the second abrasive projector B, wherein the suspension member is halted and the article exposed to treatment by the stream 2). Thereafter, the suspension device is then moved to position o'pposite the projector C where it is again treated. The drive is again energized and moves the suspension device 10 and finally, the articles are carried out of the housing Ill whereafter the article E may be removed from the hook H at any convenient point,

The present; invention provides apparatus whereby 'all portions of an article may be treated to the desired extent since the article is suspended in a manner which presents the minimum interference with the'flight of the abrasive particles and the article is rotated about in the The apparatus provides positive manipulation of the articles to be treated and thus uniformity of treatment may be obtained, thereby insuring against over] or under treating. The apparatus; may be made automatic or semi-automatic and thus requires a minimum of attention on the part of an operator.

The articles are handledin a convenient and emcient manner which permits rapid loading and unloading and which insures against breakage or v damage of the Work piece since there is no jarring or tumbling. The conveyor track may, if desired, be inserted in a production-line conveyor track and thus the abrasivetreating of the caste ings and forgings may bemade an integral part of a complete production line or system.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be madeby those skilled in the art without departing from the spirit of theinvention.

What is claimed is: 1. Apparatus for blast cleaning castings, forgings and like articles which apparatus includes, relatively fixed means for establishing a stream .of abrasive particles traveling at blasting velocities, conveyor means including hangers adapted to advance articles to be cleaned through said stream in suspended position, driving means for said conveyor, control means actuated by the movement of said hangers past said control means for periodically halting said conveyor when said articles are in said abrasive stream,

and means driven independently of said advancing means for rotating each of said articles before, during and after they are in said stream.

2. Apparatus for blast cleaning castings, forgings and like articles which apparatus includes abrasive throwing wheels at a plurality of spaced stations for establishing differently directed streams of abrasive particles traveling at blasting velocities, conveyor means including hangers adapted to advance articles to be cleaned through said streams in suspended position, driving means for said conveyor, an electric motor for driving said conveyor means, electric control means actuated by the movement of said hangers past said control means for periodically halting said conveyor driving motor when said articles are in each of said abrasive streams, and means operated independently of said conveyor advancing motor for rotating each of said articles before, during and after they are in each of said streams.

3. Apparatus for blast cleaning castings, forgings and like articles which apparatus includes, means comprising an abrasive projector of the rotary centrifugal type for projecting a stream of abrasive particles at blasting velocities, conveyor means for advancing articles through said stream, said conveyor means including a stationary track, a plurality of suspension devices mounted for movement along said track, an endless drive chain connected to said suspension de-. vices for advancing said devices along a circuitous path, a'driving motor associated with said endless chain, and means for rotating said suspension devices including a driven member mounted on each of said suspension devices, a driving member driven independently of said driving motor disposed adjacent the path of and adapted to engage each of said suspension members during at least the portion of their path wherein they'pass through the abrasive stream, controlmeans having anactuating mechanism in the pathof and engageable by'said-suspension devices for controlling the energization of said motor for halting the advance movement of said suspension devices for a predetermined interval when said article under treatment is positioned each adapted'to project a stream of abrasive particles at blasting velocities in a fan-like stream,

one of said projectors being adjusted and positioned to project a stream of particles against the top and at least a portion of the side faces of an article carried by said conveyor, and another of said pro ectors being adjusted and positioned to pro ect a stream of particles against the bottom and at least a'portion of the side faces of movement of each of said suspension devices for a predetermined time interval when the article supported thereon is positioned in the path of each of said streams, said mechanism including wheel on eaC-h'side of the path of movement of the said conveyor, each of said wheels having control means associated therewith operative to direct a fan-shaped stream of abrasive against the article moved into the path of said streams and between said wheels, a housing enclosing said streams and the article under treatment, means for rotating said suspension device when the article supported thereby is within the path of each vice rotatably connected to said carriage for rotatably suspending the article to be cleaned, an abrasive throwing wheel on each side of said track and positioned below the same, each of said wheels having control means associated therewith operative to direct a fan-shaped stream of abrasive against the article moved into the path of said streams and between said wheels, means for rotating said suspension device when the article supported thereby is within the path of said abrasive streams, a driving element for lineally advancin said carriage, a motoroperating said driving element, a time switch operatively connected to said motor, and means connected in circuit with said time switch and said motor adapted to be engaged by said carriage to halt the operation of said motor and the linear advance movement of said carriage for a predetermined time interval while the article supported on said suspension device is positioned in each of said streams.

7. In apparatus for blast cleaning metal articles including in combination, an I-beam track, a suspended article supporting hanger movable along said track, said hanger including paired rollers running on said track, a U-bracket suspended from said paired rollers having a downwardly extending shank extension, a bearing collar fixed to said shank extension, a thrust hearing supported by said collar, a suspension rod supported by said thrust bearing extending downwardly substantially in vertical alignment with said track, said suspension rod having a hook portion at the lower end thereof from which articles may be suspended, and an endless hanger driving chain having a run thereof extending under said track, means for securing said hanger driving chain to said bracket, a fixed guide memher for supporting said run of the hanger driving chain in position generally parallel to said track, means for driving said hanger chain, a sprocket fixed to said suspension rod below said bearing collar, a continuous sprocket driving chain having one run thereof extending along said track in position for engagement with said sprocket,

chain to rotate said suspension rod and the article suspended therefrom, and a U-shaped guide member extending along the sprocket engaging run of said sprocket chain preventing lateral displacement thereof in one direction and exposing said sprocket chain to engagement from the opposite direction of said sprocket.

8. In apparatus for blast cleaning metal articles including in combination, a circuitous overhead track, a suspended'article supportin hanger movable along said track, said hanger including paired rollers running on said track, a U-bracket suspended from said paired rollers having a downwardly extending shank extension, a bearing collar fixed to said shank extension, a thrust bearing supported by said collar, a suspension rod supported by said thrust bearing extending downwardly substantially in vertical alignment with said track, said suspension rod having a hook portion at the lower end thereof from which the articles may be suspended, and an endless hanger driving chain having a run thereof extending under said track, means for securing said chain to said bracket, a stationary guide member for supporting said run of the hanger driving chain in a position generally parallel to said track, spaced elements for suspending said guide member from said track, means for driving said hanger chain, a sprocket fixed to said suspension rod below said bearing collar, a continuous sprocket driving chain having one run thereof extending along said track in position for engagement with said sprocket, means for independently driving said sprocket chain to rotate said suspension rod and the articles suspended therefrom, and a guide member extending along the sprocket engaging run of said sprocket chain preventing lateral displacement thereof in one direction and exposing said sprocket chain to engagement from the opposite direction of said sprocket.

CHARLES HAYWARD HAMMELL. 

